Question

I want to return rj: Object below, and I have an index key to match, kid: 1. What’s the best/fastest way of doing considerg the main Object can contain > 10k items?

Object
 coord: MM.Coordinate
 data: Object
 geometry: Object
 properties: Object
   kid: 1            <== index id
   rj: Object        <== object i want
   __proto__: Object
__proto__: Object
element: HTMLDivElement
location: MM.Location
touch: true
__proto__: Object

Answer 1

If you need to find many objects, you can build a lookup table. Iterate over your collection of main objects, and store them in an key-value-map (simple object) by their identifier:

var mainsByKid = {}; // if the keys are integers (and not sparse), use an array
for (var i=0; i<mains.length; i++) {
     var main = mains[i],
         key = main.properties.kid; // must be unique
     mainsByKid[key] = main;
}

Now you can simply access your object by

mainsByKid[1];